KR100326987B1 - Process for recovering high boiling solvents from a photolithographic waste stream comprising at least 10 percent by weight of monomeric units - Google Patents

Abstract

The present invention provides a process for recovering benzyl alcohol, gamma butyrolactone, or propylene carbonate from contaminated discharge streams during industrial processes. The waste discharge stream comprises at least about 10% by weight of monomer polymerized to form polymers with oligomers. Waste discharge streams also generally include oxidation, hydrolysis, and / or other decomposition products of high boiling solvents. The first step in the recovery process is to polymerize the monomers present in the waste discharge stream under conditions effective to reduce the concentration of monomers in the waste discharge stream to about 10% by weight or less. The waste stream is then subjected to a suspension comprising (i) a gas stream of water, soluble gases, and volatile contaminants, and (ii) high boiling solvents, semi-volatiles, and non-volatile contaminants and other substances. It is supplied to the first separation stage divided into. The water is then removed and the suspension comprising a solvent having a low vapor pressure and a high boiling point can be distilled or evaporated in a filmed evaporator which has been wiped to separate the high boiling solvent from the non-volatile material. have. In the second separation step, the solvent-containing suspension is divided into (i) solvent-containing aliquots, and (ii) sludge aliquots. The sludge fraction contains a non-volatile material in a solvent having a high boiling point.

Description

{PROCESS FOR RECOVERING HIGH BOILING SOLVENTS FROM A PHOTOLITHOGRAPHIC WASTE STREAM COMPRISING AT LEAST 10 PERCENT BY WEIGHT OF MONOMERIC UNITS}

Photolithography plays an important role in the field of printed circuit packaging. Photolithography is a method used to define areas on a photoresist thin film where copper is selectively etched to form a circuit removal method, or where copper is plated selectively to additionally form a circuit. Photolithography is also used to individualize soldermasks or dielectric layers.

There are basically two types of photoresist: negative etching and positive etching. Both positive and negative photoresists are formed from monomers (also referred to as 'monomeric units'), such as ethers of acrylate and bisphenol A. Examples of such monomers mainly used in conventional photoresists include the following compounds: t-butyl acrylate, 1,5-pentanediol diacrylate, N, N-diethylaminoethyl acrylate, ethylene glycol di Acrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, hexamethylene glycol diacrylate, 1,3-propanediol diacrylate, decamethylene glycol diacrylate, decamethylene glycol dimethacrylate , 1,4-cyclohexanediol diacrylate, 2,2-dimethylolpropane diacrylate, glycerol diacrylate, tripropylene glycol diacrylate, glycerol triacrylate, trimethylolpropane triacrylate, pentaeryth Lithol triacrylate, polyoxyethylated trimethylolpropane triacrylate, and trimethacrylate Compounds similar to those described in US Pat. No. 3,380,831, 2,2-di- (p-hydroxyphenyl) -propane diacrylate, pentaerythritol tetraacrylate, 2,2-di (p-hydroxyphenyl) -Propane dimethacrylate, triethylene glycol diacrylate, polyoxyethyl-2,2-di (p-hydroxyphenyl) -propane dimethacrylate, di- (3-methacryloxy- of bisphenol-A 2-hydroxypropyl) ether, di- (2-methacryloxyethyl) ether of bisphenol-A, di- (3-acryloxy-2-hydroxypropyl) ether of bisphenol-A, di- of bisphenol-A (2-acryloxyethyl) ether, di- (3-methacryloxy-2-hydroxypropyl) ether of tetrachloro-bisphenol-A, di- (2-methacryloxyethyl) of tetrachloro-bisphenol-A Ether, tetra-bromo-bisphenol-A, di- (3-methacryloxy-2-hydroxypropyl) ether, tetrabromo-bisphenol-A Di- (2-methacryloxyethyl) ether of 1,4-butanediol di- (3-methacryloxy-2-hydroxypropyl) ether of di- (3-methacryloxy-2 of diphenolic acid -Hydroxypropyl) ether, triethylene glycol dimethacrylate, polyoxypropyltrimethylol propane triacrylate, ethylene glycol dimethacrylate, butylene glycol dimethacrylate, 1,3-propanediol dimethacrylate , 1,2,4-butanetriol trimethacrylate, 2,2,4-trimethyl-1,3-pentanediol dimethacrylate, pentaerythritol trimethacrylate, 1-phenyl ethylene-1, 2-dimethacrylate, pentaerythritol tetramethacrylate, trimethylol propane trimethacrylate, 1,5-pentanediol dimethacrylate, diallyl fumarate, styrene, 1,4-benzenediol dimetha Acrylate, 1,4-diisopropenyl benzene and 1,3,5-triisopropenyl benzene.

In addition to the reactive monomers mentioned above, the photoimageable compositions used in negative and positive photoresists may also include one or more free radical-initiating and polymerizable species having a molecular weight of about 300 or more. have. Such monomers include alkylene or polyalkylene glycol diacrylates and compounds described in US Pat. No. 2,927,022. Specific thickeners such as silica, clays, alumina, bentonite, carlonite and the like may also be used in the composition capable of forming the photoimage. Dyestuffs, pigments and the like may also be added to increase the visibility of the resist image. However, all colorants used must be transmitted to actinic radiation used to polymerize the monomers. In some compositions, it is desirable to add plasticizers to give flexibility to the film or coating, which may be either solid or liquid. In general, an inert solvent volatile at normal pressure may be used to prepare these photoresist compositions.

In addition, a composition capable of forming a photo image may be used to form a solder mask. Such compositions include acrylic monomers or epoxy monomers, free radical initiators, and thermal crosslinkers. Photoimageable solder mask compositions comprising the acrylic monomers and free radical initiators described in U. S. Patent No. 5,026, 624 assigned to the applicant of the present invention are incorporated herein by reference and form part of the present invention. Photoimageable solder mask compositions comprising cationic polymerizable epoxy monomers and cationic photoinitiators are described in US Pat. No. 5,300,402.

During the processing of the photoresist or solder mask, a film capable of forming an acrylate-based or epoxy-based photoimage is first applied to a circuit board and then patterned by irradiating actinic rays to a preselected area. To develop a pattern of polymerized and unpolymerized material, the coated plate is contacted with the liquid developer by either dipping or spraying. N.R. on Photoresist Development and Strip Solvent Compositions and Methods for Their Use. Bantu, Anilkumar Bhatt, Ashwinkumar Bhatt, G.W. Jones, J.A. Kotylo, R. F. Owen, K.I. Papathomas, and A.K. U.S. Patent No. 5,268,260 to Vardya discloses a low vapor pressure and high boiling point benzyl alcohol, gamma butyrolactone, for developing acrylic photoresists such as Dupont Riston T-168 and solvent-processable solder masks such as Vacrel 700 and 900. And the use of propylene carbonate. In the case of negative photoresists, the unpolymerized material used to form the photoresist, ie the acrylate or epoxy monomer, is dissolved in the developer at a low temperature, preferably at a temperature of 15 ° C to 45 ° C. Positive resists do the opposite. The actinic rays allow the positive photoresist to dissolve better in the developer, and the irradiated area is predominantly removed by the developer.

Dissolved materials and developing solutions, consisting primarily of acrylate or epoxy monomers, are removed from the circuit board by allowing the solution to flow out of the contamination tank. In order to further improve the development of the pattern, the remaining dissolved material and developing solution are preferably washed out of the circuit board with hot water. High vapor pressure organic solvents such as isopropyl alcohol, acetone, methyl ethyl ketone, and xylon may also be used as cleaning agents. The effluent produced in this process is a contaminated solution in a developer that contains a lot of monomers and other impurities. Generally the release comprises at least 10% by weight monomer.

Large volumes of liquid waste, including impure benzyl alcohol, propylene carbonate, or gamma butyrolactone, are released during the development process described above. This liquid waste must be further disposed of (eg by incineration) before it is released to the outside. Such a method of treating liquid waste is expensive. Moreover, the industrial costs of purchasing clean materials, namely pure benzyl alcohol, gamma butyrolactone and propylene carbonate, and the environmental costs of producing pure materials are also significant.

Thus, there is a need for new methods of reducing the amount of solvent containing waste generated in these or other industrial processes. Particularly preferred is a method that allows the recovery of relatively pure solvents that can be reused by industry so that there is no need to purchase pure materials.

It is an object of the present invention to provide a process for recovering benzyl alcohol, gamma butyrolactone and propylene carbonate from impure effluent waste in industrial processes.

1 is a flow chart illustrating a method for recovering a low vapor pressure and high boiling point solvent from a waste stream comprising at least about 10% by weight monomer, such as acrylate.

2A-2B are schematic diagrams illustrating polymerization apparatus useful for reducing the concentration of monomers comprised in a waste discharge waste stream.

3 is a cross-sectional view of a single stage vertical tube heat exchanger type evaporator for separating solvent from water and volatiles.

4 is a cross-sectional view of a wiped film type evaporator for separating solvent from non-volatile and contaminants.

5 is a schematic of a stripping apparatus for separating a solvent from a semi-volatile material.

6 is a cross-sectional view of a packed column evaporation column for separating solvent from decomposition products of solvents and other high vapor pressure contaminants.

The present invention provides a process for recovering benzyl alcohol, gamma butyrolactone and propylene carbonate from contaminated release waste in industrial processes. The waste discharge stream comprises at least about 10% by weight monomer that reacts to form oligomers and polymers. Waste discharge streams also generally include oxidation, hydrolysis, and / or other decomposition products, which are one of the high boiling solvents. As such, the waste discharge stream comprising benzyl alcohol also includes benzoic acid and / or benzaldehyde. Industrial process waste discharge streams comprising gamma butyrolactone also typically comprise gamma-butyric acid and / or hydroxybutyric acid. Industrial process discharge streams comprising propylene carbonate also include propylene glycol, propylene oxide, and carbon dioxide. Such waste discharge streams are produced when benzyl alcohol, gamma butyrolactone and propylene carbonate are used as developer in the photolithography process.

The first step of the recovery process includes a method of polymerizing monomers present in the waste discharge stream under conditions effective to reduce the concentration of monomers contained in the waste stream up to about 10% by weight. The waste stream is then separated into a suspension comprising (i) a gas stream of water, soluble gases, and volatile contaminants, and (ii) high boiling solvents, semi-volatiles, and non-volatile contaminants and other substances. Is supplied to the first separation stage. This first separation step lowers the concentration of water in the suspension to a level that substantially avoids the further hydrolysis of the low vapor pressure and high boiling point solvent. The low vapor pressure and high boiling point suspension, from which the water has been removed, is then distilled or evaporated in a filmed evaporator which is wiped to separate the high boiling solvent from the non-volatile material. In the second separation step, the suspension containing the solvent is divided into (i) solvent-containing aliquots, and (ii) sludge aliquots. The sludge fraction contains a non-volatile material in a solvent having a high boiling point.

In industrial processes using relatively pure benzyl alcohol, propylene carbonate, or gamma butyrolactone as developer to remove unpolymerized material from photoprocessed photoresist or soldermask films, respectively, contaminated benzyl alcohol, propylene carbonate or Generates gamma butyrolactone-emitting waste. Such discharge wastes are generally (i) at least 50% by weight of high boiling solvents, generally from about 85% to about 97% by weight of high boiling solvents, (ii) up to about 20% by weight of monomers, generally From about 10% to about 15% by weight of monomer, (i) up to about 5% by weight of decomposition products of solvents having high boiling points, generally from about 0.05% to about 1% by weight, (iv) plasticizers, Other components (referred to herein as other 'materials') in the composition capable of forming up to about 10% by weight of the photoimage, such as dyes, initiators, thickeners, or thermal curing agents, and (iii) about 20% by weight Up to about 5% by weight of water in general. These weight percentages should be 100% by weight in total, but may be up to 100% by weight if other impurities are present.

The present invention exemplarily describes a method for recovering benzyl alcohol, propylene carbonate or gamma butyrolactone from a waste stream, but 1-benzyl alcohol, benzyl t-butanol, 2-benzyloxy ethanol, 5-phenyl-1 It is, of course, also applicable to other aromatic alcohols such as -pentanol, phenyl ethyl alcohol, 3- (n-benzyl-n-methyl amino) -1-propanol. Appropriate temperatures and pressures for recovering these aromatic alcohols according to the present invention can be readily determined within the skill of the art.

It is necessary to recover the pure solvent in order to recycle the low vapor pressure and high boiling point solvent for reuse as a developer or stripping agent. The pure solvent is generally 99% by weight or more pure when analyzed by gas chromatography; Monomers and other substances are essentially removed; Up to about 0.1% by weight, preferably up to about 0.05% by weight of water, and up to 0.01% by weight of solvent decomposition products.

1 is a flow chart illustrating an example of a process for recovering a low vapor pressure and high boiling point solvent from a waste discharge stream, the solvent being used as a developer. This waste discharge stream contains monomers such as solvent, water, acrylates, acrylate esters or epoxy intermediates bisphenol A, decomposition products of the solvent, and other materials. The waste discharge stream comprises at least about 10 wt% or more monomers, and may comprise up to about 20 wt% monomers.

In the recovery process illustrated in FIG. 1, the first step includes feeding a waste stream to the polymerization apparatus to polymerize substantial monomers in the waste discharge stream. Reducing the concentration of monomers in the waste discharge stream by up to about 5% by weight. The polymerization may be effected by heating or preferably by irradiating the stream with actinic radiation for a time sufficient to cause. Preferably, as shown in FIG. 2, the polymerization apparatus is a glass tube through which actinic radiation is transmitted. The waste discharge stream exiting the polymerization stage comprises (i) about 85% to about 97% by weight of solvent, (ii) up to 10% by weight of monomer, generally about 1% to about 5% by weight of monomer, ( Iii) about 10% to about 25% by weight of the 'polymerization product', (iii) about 0.05% to about 1% by weight of solvent decomposition products, and (iii) about 0.05% to 5% by weight of water do. The 'polymerization product' is a mixture of polymers of various lengths, including soluble, non-filtration, non-settleable, fluid-like small polymers, and large polymers having insoluble, isolated solid particles. In some instances the polymerization product becomes a gelatinous mass that cannot be filtered. Chemically compatible materials, such as diatomaceous earth, are added to the polymerization product to improve filterability. Optionally, the polymerization can be stopped by adding a quinone-type stabilizer.

The waste discharge stream is then fed to a dewatering unit, which is the first separation step. The waste discharge stream in the first separation stage comprises (i) a gaseous stream of water and volatiles removed at the top of the evaporator 21 and (ii) a solvent having a high boiling point at the bottom of the evaporator 21. Is separated into two streams of liquid stream. As the water removing apparatus, as shown in FIG. 3, a short tube vertical pipe heat exchanger type evaporator may be used. Alternatively, the first stage separator can be a boiling pot, flash evaporator, or other type of heater for removing the vapor stream containing water from the liquid solvent-containing stream. have.

This first separation step lowers the concentration of water in the liquid stream to a level low enough to substantially avoid hydrolysis of the solvent having a low vapor pressure and high boiling point to the corresponding decomposition product. In a first stage separator, such as a heat exchanger type evaporator 21, the total pressure is maintained higher than the vapor pressure of the solvent at the open cup flash point. The waste discharge stream comprising benzyl alcohol in the first stage separator is thus maintained at a temperature of about 80 ° C. to about 90 ° C., and the total pressure of the evaporator 21 is maintained at a level of about 15 torr to about 25 torr. . If the waste discharge stream comprises gamma butyrolactone, the temperature of the waste stream is maintained at about 75 ° C. to about 85 ° C., and the pressure in the evaporator 21 is maintained at a level of about 20 to about 35 torr. If the waste discharge stream comprises propylene carbonate, the temperature of the waste stream is maintained at about 115 ° C to about 125 ° C and the pressure in the evaporator 21 is maintained at a level of about 25 torr to about 35 torr.

The bottom product of the first separation stage is (i) about 90% to about 98% by weight of each solvent, (ii) about 10% to about 25% by weight of the polymerization product and other materials , (Iii) from about 0.03% to about 1% by weight of decomposition products of the solvent, and (iii) from about 0.03% to about 0.1% by weight of water.

The solvent from which water is removed in the first separation step is preferably distilled or evaporated in the washed film type evaporator 41 to separate the solvent from the non-volatile contaminants. When the solvent from which the water is removed includes benzyl alcohol, the pressure of the evaporator 41 is maintained at about 15 torr or less, preferably about 5 to about 11 torr, and the temperature is about 81 to about 95 ° C. maintain. When the solvent from which the water is removed includes propylene carbonate, the pressure of the evaporator 41 is maintained at about 30 torr or less, preferably about 6 to about 22 torr, and the temperature is about 116 ° C to about 127 ° C. maintain. When the solvent from which the water is removed includes gamma butyrolactone, the pressure of the evaporator 41 is maintained at about 25 torr or less, preferably about 8 to about 20 torr, and the temperature is about 76 ° C to about 93 Maintained at ° C. In this step, the solvent from which the water has been removed is separated into a solvent-containing vapor fraction and a sludge fraction. The sludge fraction, ie the bottom product, contains inert contaminants such as fillers and non-volatile contaminants such as benzoic acid in each solvent. The solvent-containing vapor fraction obtained in this second separation step, ie the product on top, is about 95 to about 99% by weight of solvent.

The upper product, i.e., the solvent-containing vapor fraction separated from the water and evaporated, is fed to a stripping unit 71 which is filled with a mass transfer device 71 as shown in FIG. It can also be Semi-volatile contaminants such as plasticizers and residual monomers in the stripping apparatus are removed from the vapor using a cooled, compatible liquid solvent such as a mass transfer medium. By “cooling” is meant here the temperature of the mass transfer medium is at least about 20 ° C. below the temperature of the vapor. Preferably it means that the temperature of the mass transfer medium is from about 35 ° C to about 70 ° C. Preferably, the mass ratio of mass transfer medium to vapor is about 1: 7.

In stripping apparatus 71 heat from the evaporated semi-volatile contaminants is transferred to the mass transfer medium. Such delivery causes semi-volatile contaminants to condense into the liquid and this is removed from the vapor stream. At the same time a small amount of mass transfer medium is evaporated and introduced into the product stream. Thus, in order to avoid introducing other contaminants into the vapor fraction, it is preferred that relatively pure benzyl alcohol be used as the mass transfer medium when benzyl alcohol is the primary solvent in the waste stream.

The top product of this stage is a solvent-containing vapor that condenses into a removed solvent fraction comprising at least about 96% by weight solvent. The bottom product is a liquid comprising a mass transfer medium and semi-volatile species. If the mass transfer medium used and the recovered solvent are the same, it is preferable to return the bottom product to the first stage evaporator 21 to increase the recovery of each solvent.

Depending on the degree of pureness required, the removed solvent aliquot can be stored for future use or for further purification. The purification may be carried out by feeding the removed solvent-containing fraction into a fractioning unit 81, which may be a packed column of the type shown in FIG. The fraction containing the solvent removed in the fractionation device 81 is characterized by high vapor pressure, low boiling point of the upper product (fractionated waste) and low vapor pressure, high boiling point of the lower product (herein referred to as 'final solvent product'). Mentioned). The reboiler heats the fluid that is collected and recycled back to the bottom of the fractionator 81. The cooled condensate is introduced to the top of the fractionation device 81.

In these examples where the aliquots containing the solvent removed include benzyl alcohol, the top pressure of the fractionating device 81 is about 10 torr or less, and generally about 1 to about 4 torr, and the bottom pressure is About 25 torr or less, and generally about 10 to about 20 torr. The top product of this process is benzaldehyde and the bottom product is about 99% or more pure benzyl alcohol. In these examples in which the aliquots containing the removed solvent comprise propylene carbonate, the upper pressure of the fractionating device 81 is about 15 torr or less, and generally about 4 to about 10 torr, and the lower pressure is About 25 torr or less, and generally about 15 to about 20 torr. The top product of this process is water and propylene glycol and the bottom product is about 99% or more pure propylene carbonate. In these examples in which the aliquots containing the solvent removed include gamma butyrolactone, the top pressure of the fractionation device 81 is about 10 torr or less, and generally about 2 to about 5 torr, and preferably The pressure is about 25 torr or less, and generally about 15 to about 20 torr. The top product of this process is hydrobutyric acid and the bottom product is about 99% or more pure gamma butyrolactone.

The product of fractionation apparatus 81, ie the final solvent product, is about 99% by weight or more solvent and essentially does not contain other materials, photoresist products, and other solids. In addition, the final solvent product includes up to about 0.03% by weight of water and about 0.01% by weight of decomposition products, so that decomposition products of water and solvent are essentially removed.

Optionally, a solvent having a low vapor pressure and a high boiling point can also be recovered from the bottom product of the evaporator 41, ie the sludge fraction. The bottom product contains inert contaminants such as fillers, and non-volatile contaminants such as benzoic acid corresponding to each solvent. The bottom product comprises about 70 to 95 weight percent solvent, balance solid. In this optional step the bottom product of the evaporator 41 is fed to an additional evaporator 61. The top product of the second evaporator is introduced into the stripper 71 as shown in FIG. The bottom product of the evaporator 61 is a substance containing a large amount of polymer that is discharged and collected into a storage tank or drum. If the collected waste product comprises at least about 20% by weight reactive monomer, preferably about 5 ppm to about 500 ppm of an antioxidant or stabilizer is added to the collected waste product. Examples of such stabilizers include hydroquinone, p-methoxy phenol, alkyl substituted hydroquinone, aryl substituted hydroquinone, t-butyl catechol, pyrogallol, naphthylamine as well as copper organometallic compounds. , Quinone type stabilization such as beta-naphthol, 2,6-di-t-butyl-p-cresol, phenothiazine, pyridine, nitrobenzene, dinitrobenzene, p-toluene quinone, hydroquinone monomethyl ether I am.

Optionally, all process steps are performed under a blanket of nitrogen to reduce combustion potential. Using a nitrogen blanket provides a product with better physical properties. Alternatively, about 5 ppm to about 500 ppm of stabilizer is added prior to processing in evaporator 21 or evaporator 41 or prior to shipping the waste. The addition of stabilizers can prevent exothermic reactions that occur during various processing steps and during shipping or storage of waste. It is particularly desirable to add such stabilizers when each waste stream or waste product comprises at least about 20% by weight reactive monomers.

In each processing step, the first processing step wherein at least 10% by weight of the emitted waste comprises monomers is a polymerization step of the monomers. As shown in FIG. 2, the polymerization reaction is carried out in a polymerization apparatus 11, which comprises a vessel 12 which transmits actinic radiation, ie ultraviolet light of a specific emission wavelength. Vessel 12 is attached or adjacent to actinic radiation source 13.

The waste stream 15 is polymerized by irradiation with actinic radiation from the actinic source 13 for a temperature and time sufficient to cause crosslinking of the monomers and to reduce the concentration of monomers in the waste stream 15 to 10 wt% or less. It is introduced into the container 12 of the device 11. For waste streams comprising acrylate monomers, the preferred wavelength is about 365 nm; The preferred wavelength for the epoxy monomer is about 1000 nm. The temperature in vessel 12 is maintained at about 20 ° C to about 100 ° C. The irradiation time of actinic radiation to the waste stream 15 depends on the concentration of monomers in the stream, the composition of the stream and the fluid properties of the stream, the presence of interfering compound species such as dyes, the temperature used, the UV addition rate, and the Depending on fouling of the permeate surface, it may be from about 5 minutes to over 24 hours. The waste discharged from the polymerization apparatus 11 comprises up to 10% by weight of monomer and from about 10% to about 25% by weight of polymerization product.

The discharge waste is then fed to a water removal device 21 which is a short tube vertical heat exchange type evaporator 21, such as a falling film type evaporator, which is shown in FIG. Is shown. The short tube vertical heat exchange type evaporator 21 comprises a feed stream 22 in the evaporator 21 which is separated into a lower liquid stream 23 and an upper gas stream 24. Water, for example deionized water, may also be supplied to the top of the evaporator. The heat transferred from the gas stream to this water helps to condense the solvent vapor, ie benzyl alcohol, gamma butyrolactone, or propylene carbonate in the gas stream, thereby reducing the loss of the desired solvent to the top 24.

The stream enters heat exchanger type evaporator 21 through stream inlet 31, which is an inlet to shell and tube type heat exchanger 21. The stream is a shell side medium. In one example, the tube 39 is a vapor riser. The evaporating feed rises through a tube or steam riser 39. Stream condensate exits the shell and tube heat exchanger 31 through outlet 33.

The total pressure in the vertical heat exchanger type evaporator 21 is maintained above the vapor pressure of the solvent at the open cup flash point. The temperature of feed stream 22 is raised to a temperature about 2-10 ° C. below the open cup flash point of the solvent, thereby igniting water and other volatile species and gases of the liquid stream. The waste discharge stream comprising benzyl alcohol in the first stage separator is thus maintained at a temperature of about 80 ° C. to about 90 ° C. and the total pressure is maintained at about 15 to about 25 torr. If the waste discharge stream comprises gamma butyrolactone, it is maintained at a temperature of about 75 ° C. to about 85 ° C., and the total pressure in the evaporator 21 is maintained at about 20 to about 30 torr. If the waste discharge stream comprises propylene carbonate, it is maintained at a temperature of about 115 ° C to about 125 ° C and the total pressure in the evaporator 21 is maintained at about 25 to about 35 torr.

The liquid product 23 of the first separation step 21 is then fed to the second separation step 41. The second stage separator 41 is a single-effect wiped film evaporator as illustrated in FIG. 4.

The cleaned film type evaporator 41 includes a cylindrical vessel 42 as a steel vessel. The inner wall of the vessel may be metal such as stainless steel, super alloy or the like. Alternatively the inner wall may be formed of glass or enameled lines. Enamel means porcelain enamel. Enamel is an inorganic material that has been glassy or partially deglassed. The glass or enamel line is bonded to the steel vessel 42.

The cleaned film type evaporator 41 is characterized by having a rotating wiper assembly 43 extending along the vertical axis of the evaporator 41. The rotary wiper assembly 43 is provided with a rotary shaft 44, an arm 49 extending outwardly from the rotary shaft 44, and an arm 49 for spreading a solvent solution on the inner wall of the vessel 42. It includes a blade 50 located at the end.

The rotating shaft 44 is driven by a motor 45 through a bearing 46 and a coupling 47 extending through a seal 48 in the top of the container. The wall of the cleaned film evaporator 41 is heated by steam in the steam jacket 52.

In operation, the solvent from which the water of the first stage evaporator 21 has been removed is introduced into the washed film evaporator through an opening 55. The liquid feed is directed to a distributor 51. Centrifugal force and gravity direct solvent outside of the dispenser 51 to the blade 50 at the end of the arm 49. The blade 50 spreads the solvent onto the interior surface of the vessel 42, where the steam in the steam jacket 52 heats the solvent to produce solvent vapor 57. The liquid residue falls into the conical collection zone 53 and outlet 54.

The liquid product of the second separation step 41 can be further processed, for example using the bottom evaporator 61, to concentrate the resist solids and increase the solvent distillate yield. The final residue of the bottom evaporator 61 is the main processing waste. Optionally, a quinone type stabilizer can be added to this liquid product to limit the exothermic polymerization reaction. Vapors from devices 41 and 61 are solvents that are substantially free of photoresist material but contain a small amount of plasticizer and other volatile and semi-volatile materials, such as monomers, wherein less volatile components are delivered to the mass transfer medium. To the stripping apparatus 71, which is then used. The temperature of the mass transfer medium is at least about 20 ° C. or less than the temperature of the vapor, preferably from about 35 ° C. to about 70 ° C. The operating pressure in the stripping device 71 may vary from a lower pressure at which the removed solvent vapor is discharged from the stripping device to a slightly higher pressure at the bottom where the vapor stream from the evaporator 41 is introduced into the stripping device 71. Is changed.

When the solvent is benzyl alcohol, the pressure at the vapor inlet of the stripping apparatus is maintained below about 15 torr, preferably about 5 to about 11 torr. When the solvent is propylene carbonate, the pressure at the vapor inlet of the stripping apparatus is maintained below about 30 torr, preferably from about 12 to about 22 torr. When the solvent is gamma butyllactone, the pressure at the vapor inlet of the stripping apparatus is maintained below about 25 torr, preferably from about 8 to about 20 torr.

Steam 77 from the devices 41 and 61 is introduced into the vapor stripper device 71 through a vapor inlet connection 73 located near the bottom of the device shell 72. The vapor flows upwards through mass transfer contact means 75 having a random packing style, a structural packing style, a bubble tray style, or any other style that allows the vapor and liquid stripping medium to come into contact. While flowing through mass transfer contact means 75, the vapor stream is in contact with a cooled and cleaned liquid mass transfer medium flowing downstream, the liquid mass transfer medium being contacted by liquid distributor 76. Is distributed to. While flowing through the contact means 75, semi-volatile components are removed from the vapor. The removed vapor 78 is discharged from the shell of the apparatus through a vapor outlet 74 which is generally located near the top of the shell 72. The discharged liquid stripping stream 80 comprising semi-volatile species leaves shell 72 from the bottom of the apparatus. The movement of the steam in the steam stripper 71 is caused by the pressure difference in the apparatus as shown in FIG. 1, which moves from the high pressure evaporators 21 and 41 to the low pressure condenser. . Movement of the liquid stripping medium in the vapor stripper 71 is caused by gravity.

The mass transfer medium 79 should be a compatible liquid that is vapor chemically non-reactive. The mass transfer medium 79 should be selected such that the semi-volatile species dissolve in the mass transfer medium 79 at the conditions and concentrations present in the vapor stripping apparatus 71 during processing of the vapor stream.

The solvent vapor obtained from the stripping device 71 is condensed into the removed liquid solvent product which can be stored for later use. Optionally, a portion of the removed liquid solvent is recycled back to stripping apparatus 71 for use as mass transfer medium 79.

The removed liquid solvent product is introduced into fractionation column 81 for further purification. Components more volatile than solvent in the fractionation column 81 form a vapor phase that is removed from the top of the column and then condensed. The components in the vapor phase include the decomposition products of water and the solvent recovered. Examples of decomposition products of high boiling solvents are benzaldehyde, hydroxybutyric acid, gamma butyric acid, propylene glycol and propylene oxide.

Fractionation takes place in this apparatus, where more volatile species move to the top of column 81 to condense, and less volatile solvent is cooled as a liquid cooler than its boiling point. Circulate inside the floor. General methods of steam column operation, including the adjustment of the top reflux rate and the bottom reheat rate, apply. Condensation can be effected effectively by the reflux stream introduced at the top of the column 81. A liquid stream comprising solvent is discharged at the bottom of column 81. This stream is removed from the system and stored as the final solvent product. Alternatively, the liquid stream is introduced into a reheater, which heats the liquid and vaporizes the more volatile contaminants again. The vapor product from the reheater is introduced back to the fractionation column for further purification.

If the solvent removed is benzyl alcohol, the operating pressure of column 81 varies from about 1 to about 4 torr at the top and from about 10 to about 20 torr at the bottom. If the solvent removed is gamma butyrolactone, the operating pressure of column 81 varies from about 2 to about 5 torr at the top and from about 15 to about 20 torr at the bottom. If the solvent removed is propylene carbonate, the operating pressure of column 81 varies from about 4 to about 10 torr at the top and from about 15 to about 20 torr at the bottom.

Packed column steam column 81 is shown in detail in FIG. 6. Structurally, the packed tower 81 includes a shell or body 82 having a condenser 85 at the top and a reheater 91 at the bottom. Feed is introduced into the liquid distributor 86 and the packing restrainer 87 inside the tower 81 via liquid supply means 83; The feed position is about one half of the tower height. The liquid distributor 86 and the charge restrictor 87 distribute the feed and condenser return 84 on or through the surface of the fill 95.

The gas flowing upwards, such as, for example, return 88 from reheater 91, contacts liquid flowing downstream, condensed by condenser heat exchanger 94 and has a high vapor pressure and low boiling point 99. ), The upper product 93 in the condenser 85 having a low boiling point and high vapor pressure recovered as), and the product in the reheater 91 having a high boiling point and low vapor pressure recovered in the liquid product 96. . Residual liquid in the reheater is vaporized by heat exchanger 97. The final solvent product suitable for reuse in the manufacturing process exits the bottom of the fractionation column 81 or from the liquid product 96.

Although the present invention has been described with reference to preferred embodiments or examples, it may also be used to purify solvents obtained in other industrial processes. Thus, the process described herein is intended to purify low vapor pressure and high boiling solvents from waste streams comprising ionic and contaminants, coloring materials, polymers, oils, paints, carbons, and resins, as well as photoresist materials. May also be used. The scope of the invention is not limited to the above preferred embodiment but only by the appended claims.

The present invention provides a method for the efficient recovery of solvents with low vapor pressure and high boiling point from contaminated waste discharge streams during industrial processes.

Claims (22)

A process for recovering said low vapor pressure and high boiling point solvent from a waste discharge stream comprising a low vapor pressure and high boiling solvent, water, and at least 10 wt% monomer (a) polymerizing monomers in the waste discharge stream under conditions effective to reduce monomers in the waste discharge stream to 10% by weight or less; (b) feeding the waste discharge stream to a first stage separator and separating water and volatiles from the waste discharge stream to provide a solvent separation from which water has been removed; And (c) supplying the solvent fraction from which the water has been removed to a second stage separator, and discharging the solvent fraction from which the water is removed to a vapor fraction containing a solvent having a low vapor pressure and a high boiling point and a sludge containing a non-volatile substance. Separation into aliquots Solvent recovery method comprising a. The method of claim 1, wherein the solvent is selected from the group consisting of aromatic alcohols, gamma butyrolactone, and propylene carbonate. The method of claim 1, further comprising removing semi-volatile species from the vapor fraction to provide a liquid solvent. 4. The method of claim 3, further comprising separating the liquid solvent into a high vapor pressure fraction comprising a substance that is more volatile than the solvent and a low vapor pressure fraction comprising the solvent. 2. The method of claim 1, further comprising separating the vapor fraction into a high vapor pressure fraction comprising a substance that is more volatile than the solvent and a low vapor pressure fraction comprising the solvent. The process of claim 1 wherein said polymerizing step (a) consists of irradiating said waste discharge stream with actinic radiation. The method of claim 1 wherein the temperature is maintained below the open cup flash point of the solvent. The method of claim 1 wherein the solvent is benzyl alcohol and the pressure of the first stage separator is maintained at about 25 torr or less. The method of claim 2, wherein the aromatic alcohol is benzyl alcohol. The method of claim 1, wherein the first stage separator is a heat exchanger type evaporator. The method of claim 1 wherein the second stage separator is a wiped film evaporator. The process of claim 1 wherein at least one of (a), (b), and (c) is carried out under a nitrogen blanket. The process of claim 1 wherein about 5 ppm to about 500 ppm of stabilizer is added to the waste stream prior to step (b). 4. The method of claim 3 wherein the semivolatile species are removed from the vapor fraction by contacting the vapor fraction with a mass transfer medium. The method of claim 14 wherein the mass transfer medium comprises a solvent selected from the group consisting of benzyl alcohol, propylene carbonate, and gamma butyrolactone. The method of claim 14 wherein the solvent is benzyl alcohol and the mass transfer medium comprises benzyl alcohol. A process for recovering aromatic alcohol from a waste discharge stream comprising at least 10 wt.% Monomer (a) polymerizing monomers in the waste discharge stream under conditions effective to reduce monomers in the waste discharge stream to 10% by weight or less; (b) feeding said waste discharge stream to a heat exchanger type evaporator and separating water and volatiles from the aromatic alcohol to provide an aromatic alcohol-containing liquid from which water has been removed; And (c) the aromatic alcohol-containing liquid from which the water has been removed is evaporated in an evaporator to separate the aromatic alcohol from the non-volatile material, from which the vapor fraction comprising the aromatic alcohol and non-volatile species in the aromatic alcohol are contained. Recovering sludge fraction Aromatic alcohol recovery method comprising a. 18. The method of claim 17, further comprising removing semi-volatile species from the vapor fraction of step (c) to provide a removed vapor fraction comprising the aromatic alcohol and a liquid fraction comprising the semi-volatile species. Aromatic alcohol recovery method comprising a. 19. The method of claim 17 or 18, wherein the aromatic alcohol is benzyl alcohol. 20. The method of claim 19, further comprising separating the removed vapor fraction in a fractionating unit into a high vapor fraction comprising benzaldehyde and a low vapor fraction comprising benzyl alcohol. 18. The method of claim 17, further comprising separating the sludge fraction to recover the sludge fraction of step (c) and recover the aromatic alcohol therefrom to provide waste sludge. 22. The method of claim 21, wherein about 5 ppm to about 500 ppm stabilizer is added to the waste sludge.